U.S. Gulf Coast: Home of CO2 storage

Giant sedimentary basins underneath the United States have the capacity to store 500 years’ worth of the country’s energy-related carbon dioxide emissions, and the biggest are located in the traditional petroleum producing states along the Gulf Coast, according to U.S. government scientists.

Capturing carbon dioxide (CO2) emissions from large stationary sources like power plants and cement factories and storing them deep underground in porous rock formations is “critical” for reducing greenhouse gases according to the International Energy Agency.

“There is no climate friendly scenario in the long-run without carbon capture and storage (CCS),” the agency wrote earlier this year.

The technologies to separate CO2 from the exhaust emissions of power plants and factories, compress it into a supercritical fluid, pipe it to a storage site, then pump it into rock formations thousands of feet below the surface are all moderately mature, though deployment has been slow.

Nonetheless, the U.S. government report points to the enormous potential. In 2011, energy-related CO2 emissions in the United States amounted to 5.5 billion tonnes. But the country’s vast sedimentary basins could potentially hold 3,000 billion tonnes, enough to sequester all the country’s emissions for the next five centuries.

STORAGE RESOURCE

The findings are contained in a “National Assessment of Geologic Carbon Dioxide Storage Resources” produced by respected scientists at the U.S. Geological Survey (USGS) at the direction of Congress under the terms of the 2007 Energy Independence and Security Act.

USGS considered the volume, permeability, pore volume and other factors bearing on storage capacity for all sedimentary basins in the onshore and coastal areas of the United States to produce the most comprehensive inventory published so far of “technically accessible storage resources.”

USGS’ estimate is in line with earlier totals produced by the U.S. and Canadian governments but contains much more detail, particularly about the potential for individual storage plays.

USGS estimates the technically accessible storage resource is big enough to hold between 2,300 billion and 3,700 billion tonnes of CO2, with a confidence interval of between 5 percent and 95 percent, and a mean estimate of 3,000 billion tonnes.

Nearly two-thirds of the total (1,900 billion tonnes) is located beneath the Coastal Plains region, which stretches from Texas in the west through Louisiana, Mississippi and Alabama to Florida in the east.

The region contains seven of the ten rock formations with the greatest storage potential in the country (the others are North Dakota’s Williston Basin, Alaska’s North Slope, and the Illinois Basin).

Coastal storage resources include the Sligo and Hosston formations, under eastern Texas, Louisiana and southern Mississippi, which could hold 830 billion tonnes of captured CO2, according to USGS.

Other formations with significant potential are the Carrizo Sand (220 billion tonnes) and the Frio and Vicksburg formations (170 billion tonnes).

NOT JUST OIL FIELDS

Attention has focused on the potential for injecting CO2 into depleted oil and gas fields as part of enhanced oil recovery (EOR) operations. However, USGS estimates the amount of CO2 that could be stored in depleted petroleum fields is relatively small, just 11-15 billion tonnes.

Somewhat more CO2 could be stored in what USGS calls “buoyant traps,” where the CO2 is held in place by overhead and lateral seals, in the same way oil and gas is trapped in conventional reservoirs. Buoyant trapping resources could hold about 44 billion tonnes of CO2.

But the vast majority of the storage resource is in what USGS calls “residual traps”. Unlike buoyant traps, there is no seal. Instead, the CO2 is held as individual droplets within the pores of the rock formation by capillary forces.

The amounts of CO2 that could be stored this way are enormous. USGS estimates 140 billion tonnes could be stored in residual trapping formations with high permeability; 130 billion tonnes in formations with very low permeability; and a staggering 2,700 billion tonnes in formations with intermediate permeability.

NEW INDUSTRY BORN

Green groups are no fans of oil men. Texas, Louisiana and the other states along the U.S. Gulf Coast have a bad reputation among environmentalists as the home of the U.S. oil and gas industry, responsible for putting billions of tonnes of greenhouse-causing CO2 into the atmosphere.

Environmentalists much prefer clean, green California, with its enthusiasm for wind, solar and geothermal power, energy efficient building codes, and cap and trade programme for cutting carbon dioxide (CO2) emissions.

Of course, the contrast is a caricature. California is the third-largest oil producer after Texas and North Dakota and well ahead of Alaska. Beneath the sunny vineyards, almond trees and pistachio groves of Kern County, as well as the streets of Los Angeles, lie some of the largest oil fields in the country, pumping half a million barrels per day.

In turn, Texas, with its giant wind farms, generates more power from renewables excluding hydro than any other state. But Texas and the other Gulf states could become even more important to the green economy in future if they exploit their favourable geology to become the centre of the carbon capture and storage business.

If plans for large-scale CCS are turned into reality, the Sligo, Hosston and Carrizo formations could one day become as famous as the oil-producing Bakken shale in North Dakota and Texas’ own Eagle Ford. Sligo/Hosston could become the Ghawar of the storage business.

STATE LEGISLATION

States are already vying to attract what they hope will become a multi-billion dollar storage industry. Since 2010, legislatures in 8 different states have enacted 21 laws dealing with carbon capture and underground storage, according to the bill tracking database of the National Conference of State Legislatures.

Illinois, home to the federally-funded FutureGen project to build the first conventional coal-fired power plant with CCS, has taken the lead, enacting no fewer than 6 bills dealing with the subject.

According to USGS estimates, the Mount Simon Sandstone and Ordovician Composite formations in the Illinois Basin could store around 150 billion tonnes of CO2, positioning the state to be a potential leader in the future CCS industry.

Most aim to resolve questions about regulation, permitting, liability for CO2 escapes, and who owns the rock, or more specifically the “pore space,” into which the CO2 will be injected.

In most cases, mineral rights owners will receive payment for allowing CO2 to be stored in underground formations in the same way they now receive royalties and other payments for oil and gas production.

Strong interest in CCS in traditional oil and gas-producing states is no coincidence. While depleted oil and gas fields provide only a small proportion of total storage capacity, the same sedimentary rock formations which often contain oil and gas accumulations provide the best conditions for CO2 storage.

CCS requires many of the same technologies (from seismic surveys to high-pressure drilling) as the oil and gas industry. Traditional petroleum states have an existing engineering base that gives them an enormous advantage.

Petroleum states, with their long tradition of mineral extraction, are likely to have much more welcoming regulatory and political environments for projects that involve mineral injection.

The states along the Gulf Coast are much closer to major industrial and population centres, and therefore sources of CO2 emissions, than the remote North Slope in Alaska and Williston Basin in North Dakota/Montana.

There is a certain irony that the states which have been demonised by environmentalists for producing most of the fossil fuels that put carbon dioxide into the atmosphere, warming the planet, could in future be home to a new clean green industry designed to store emissions safely underground.